Wheels include bores that are used for assembling brake parts to the wheel in order to transmit braking force from the wheel via the bores.
Repeated braking degrades the shape of the bores. Before being degraded, each bore is a right cylinder. After being degraded, the bores become ovalized. This ovalization can generate slack between the brake part and the wheel, vibration can appear, and safety during braking can be compromised.
It is therefore necessary to restore the wheel to compliance by re-boring the bores in order to eliminate the ovalization and enable brake parts to be assembled once more in bores that are right cylinders.
These boring operations are generally performed in a workshop with the help of voluminous boring machines having fixed stands. Restoring compliance in that way is expensive and requires qualified personnel to position the wheel on the boring machine and to control the machine.